Lower back pain can be common during early pregnancy, including at 5 weeks. It is often caused by hormonal changes, the growing uterus putting pressure on the lower back, or ligament stretching. However, since you have a history of miscarriage and are taking hormone pills and blood thinners, it's important to consult your healthcare provider for an accurate diagnosis and reassurance. They can evaluate your specific situation and provide appropriate guidance based on your medical history and current condition. While some mild discomfort is normal in early pregnancy, severe or persistent pain should always be reported to your doctor as it could indicate an underlying issue that needs attention. Remember to take care of yourself both physically and emotionally during this time, seeking support from loved ones or professionals if needed.